US3593275A - Method and apparatus for the recognition of errors at the receiver in a data transmission system - Google Patents

Method and apparatus for the recognition of errors at the receiver in a data transmission system Download PDF

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Publication number
US3593275A
US3593275A US743392A US3593275DA US3593275A US 3593275 A US3593275 A US 3593275A US 743392 A US743392 A US 743392A US 3593275D A US3593275D A US 3593275DA US 3593275 A US3593275 A US 3593275A
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Prior art keywords
signal
frequencies
signals
frequency band
modulation products
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Expired - Lifetime
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US743392A
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English (en)
Inventor
Gerhard Pumpe
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Siemens AG
Siemens Corp
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Siemens Corp
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
    • H03M13/47—Error detection, forward error correction or error protection, not provided for in groups H03M13/01 - H03M13/37
    • H03M13/51—Constant weight codes; n-out-of-m codes; Berger codes

Definitions

  • the invention is particularly useful in a data transmission system in which the messages are coded in binary form at the transmitter, in one of a number m" modulation characteristics.
  • the signals to be transmitted are scanned at equal time intervals by synchronizing signals and are identified by modulation characteristics corresponding to the coding.
  • the modulation characteristics can be frequency, amplitude, or phase shift, so that one of a plurality of frequencies may be transmitted to indicate the characteristic of the signal which is being transmitted.
  • the message signals are irregular, assignment of transmission time to particular message signals is not attempted, since this is both costly and difficult.
  • irregular operation is especially suitable for reception of messages from remote stations, so that measures must be taken to decrease the added susceptibility of this type of transmission to disturbance and resulting errors.
  • the objective of the invention is achieved by use of the fact that when more than one modulation characteristic is transmitted simultaneously, modulation products occur, and these products lie outside of the frequency band in use. Consequently, in accordance with the invention, the modulation prod ucts may be filtered out and evaluated in a proper circuit, and in dependence upon that evaluation, the transmission of the decoded message at the receiver may be blocked or released.
  • FIG. I is a block diagram of a portion of the receiver of a known type of message transmission system
  • FIG. 2 shows a block diagram of a preferred embodiment of a receiver portion constructed in accordance with the invention
  • FIG. 3 is a graphic showing of modulation products occurring when two different modulation characteristics are present simultaneously within the assigned frequency band.
  • FIG. 4 is a graphic showing of the frequency spectrum in a one out of four code, in which one out of four possible modulation frequencies is transmitted at any one instant.
  • the process to be described makes it possible to recognize at the receiver errors which result in the simultaneous occurrence of two or more modulation characteristics in the received assigned or used frequency band. As indicated earlier, such errors can be caused by the input system, by the cod ing system, or by disturbances in the transmission path.
  • the error recognition process of the invention also provides protection for speech signals at the receiver, and this feature is particularly important when the data transmission occurs on a telephone channel.
  • the basic concept of the invention resides in the fact that modulation products result whenever more than one modulation characteristic, such as more than one modulation frequency, exists simultaneously. Coding errors, input errors and line disturbances can be recognized by evaluation of these modulation products.
  • FIG. 1 shows a block diagram of a portion of a known transmission system receiver for selection and demodulation of signals which are transmitted by one out of four possible frequencies.
  • the input E of the receiver supplies the modulated signal to a receiver filter EF, and the output of that filter is limited by limiter amplifier B.
  • the modulated message for THIS channel may consist of one of the four possible frequencies f-f4. Therefore, the limited signal is supplied to four different discriminators DI-D4, each of which is tuned to a different one of the four frequencies. Each discriminator emits an output signal only if the frequency to which it is tuned appears at the output of limiting amplifier B.
  • a signal will occur simultaneously at a plurality of the different outputs AIA4, rather than only in one ofthe outputs.
  • FIG. 1 shows a system for reception of a single frequency group, with four frequencies in the group. However, several different frequency groups can also be present, with only one frequency emitted in each frequency group.
  • FIG. 2 shows in block diagram form a preferred embodiment of a receiving system employing the method of the invention and constructed according to the principles of the invention for recognition of errors.
  • the received signal E is supplied through receiver filter EF and is amplified in limiting amplifier B, similarly to the system of FIG. I.
  • the limited signal is supplied not only to a discriminator system D (which may be similar to the discriminators DI-D4 of FIG. I), but that signal is also supplied to the input of a filter PI.
  • the output of the discriminator system is supplied to an amplitude evaluation circuit ABI which employs a threshold response, which can be achieved in the same fashion as in the rectifier circuit GI-Gd, of FIG. 1.
  • An output signal will appear on the output lines AI-A4, dependent upon the frequency of the signal received.
  • Filter Fl filters out the modulation products resulting from the simultaneous appearance of two different frequencies, that is, the sum and difference frequencies which lie outside of the employed or assigned frequency band. That filtered-out signal is then evaluated as to amplitude in an amplitude evaluation circuit A82. If the signal exceeds a certain threshold value, there appears at the output of the evaluation circuit, A82, a disturbance" or error signal S. This signal both supplies an indication of disturbance in the receiver and also blocks the output lines AI-A4, by control of the amplitude evaluation circuit ABI for the duration of the error. This blockage may be achieved by biasing the amplitude evaluation circuit A81 in such fashion that no outputs may be supplied to the output lines A IA4 As indicated in FIG. 2.
  • the system may also provide for the outputs of other filters corresponding to filter F1 being supplied to the amplitude evaluation circuit A82. This is indicated by connection of the input labeled F2 to the input of the evaluation circuit, indicating that the output of a filter sensitive to modulation products of frequencies in a different frequency band may be supplied to the evaluation circuit. ln such case.
  • the amplitude evaluation circuit A82 will evaluate the sum of all modulation products resulting from the individual frequency groups and will control the emission of the message at the output of the receiver. in dependence upon the level of these modulation products.
  • FIG. 3 shows a frequency spectrum resultant from the presence of a pair of frequencies or tones within the employed or assigned frequency band fN. Frequency is plotted horizontally, and the amplitude of the modulation products and the harmonic frequencies of the signals are plotted vertically.
  • the true signal Fl 1 (1.000 Hz.) is shown in the frequency band employed. If this tone or frequency were the only one supplied to the limiter amplifier. there would result if symmetrical limiting occurred, even-numbered harmonicsfl.) (2.000,
  • a disturbance or error signal 18 (M00 Hz. is shown at a spacing d from the signal tone.
  • sum tones or frequencies )6. and difference frequencies fD exist. at successive different spacings d from the signal tone and from the error tone. All of these modulation products tones may be filtered out and rejected. because they lie outside of the frequency band fN within which the signal tones must appear.
  • the filter F1 is constructed in such fashion as to block the harmonic frequencies )0 which result when only a single frequency is being received at any one instant.
  • a low-pass filter may suffice, to pass the tones having a frequency below the frequency band in use.
  • the frequency filter Fl may be selected for the lower range]! and the upper range fll so as to pass the modulation products below and above the frequency band of interestjN.
  • the amplitude evaluation circuit ABZ may be used jointly for several groups of frequencies.
  • the output lines AIA4 can be controlled by means of gate circuits in such manner that upon the presence of any disturbance. all outputs are blocked.
  • FIG. 4 shows the frequency spectrum for a one out of four code. In each case. one of the four signal tonesfl-f4 is transmitted in the employed or assigned frequency band. If two tones appear simultaneously in the frequency band. modulation products result.
  • FIG. 4 The presentation of FIG. 4 is similar to that of FIG. 3. and the amplitudes shown by the vertical lines are approximately representative of relative true magnitudes. As before. the values jO represent the harmonic frequencies. and they are ployed frequency band are employed for amplitude evaluation to indicate the presence of error signals.
  • filter means for sensing in said received signals modulation products occurring upon the appearance of more than one frequency of said predetermined group. said modulation products lying outside of the frequency band of said coded signals. but within a predetermined band width.
  • evaluation circuit means for evaluating the amplitude of the signal resulting from the said sensed modulation products and for producing an error signal when said signal resulting from said modulation products exceeds an amplitude of a predetermined value.
  • output means for said received signals and having said error signal coupled thereto.
  • said output means being adapted to be blocked to prevent the passage of said received signals thereto when said error signal is present.
  • a method for detecting errors in received data signals by using one of a predetermined group of frequencies for each code element of the signal, and wherein the disturbances caused by the actuation of more than one of said frequencies at a time are detected as errors. and comprising the steps of:
  • the limited signals being also filtered (Fl) to develop said filtered signal only from the modulation products lying outside of said assigned frequency band.
  • the said filtered signal then being evaluated as to amplitude (A82) to provide an error signal (S) when the voltage exceeds a predetermined amplitude. and said error signal when present blocks any said output signal.

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  • Physics & Mathematics (AREA)
  • Probability & Statistics with Applications (AREA)
  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Noise Elimination (AREA)
  • Radio Transmission System (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
  • Monitoring And Testing Of Transmission In General (AREA)
US743392A 1967-07-21 1968-07-09 Method and apparatus for the recognition of errors at the receiver in a data transmission system Expired - Lifetime US3593275A (en)

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DES0110937 1967-07-21

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US3593275A true US3593275A (en) 1971-07-13

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US743392A Expired - Lifetime US3593275A (en) 1967-07-21 1968-07-09 Method and apparatus for the recognition of errors at the receiver in a data transmission system

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US (1) US3593275A (de)
BE (1) BE718315A (de)
CH (1) CH476428A (de)
DE (1) DE1537338B2 (de)
FR (1) FR1574526A (de)
GB (1) GB1179378A (de)
NL (1) NL6809842A (de)
SE (1) SE337604B (de)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3771059A (en) * 1972-03-27 1973-11-06 Rca Corp Universal data quality monitor
US3885228A (en) * 1973-06-05 1975-05-20 Martin J Katz Fail-safe electronic encoder for selectively operating railway signal indicator
US4019147A (en) * 1975-12-01 1977-04-19 Physics International Company Band pass filter for impulse operation
US4092499A (en) * 1975-10-03 1978-05-30 Telefonaktiebolaget L M Ericsson Apparatus for detecting a voice frequency signal
US4305150A (en) * 1979-05-31 1981-12-08 Digital Communications Corporation On-line channel quality monitor for a communication channel
US4646097A (en) * 1985-05-06 1987-02-24 E-Systems, Inc. Off-channel frequency discriminator circuit for use in a precision distance measuring equipment (DME/P) receiver
US5142526A (en) * 1989-02-15 1992-08-25 Furukawa Electric Co., Ltd. Transmission failure diagnosis apparatus
US20040088611A1 (en) * 2002-11-01 2004-05-06 Broadcom Corporation Methods and systems for detecting symbol erasures

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3104356A (en) * 1961-04-26 1963-09-17 Earl G Hedger Fm signal-to-noise monitoring system
US3131264A (en) * 1960-04-13 1964-04-28 Int Standard Electric Corp Multi-frequency signalling receivers

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3131264A (en) * 1960-04-13 1964-04-28 Int Standard Electric Corp Multi-frequency signalling receivers
US3104356A (en) * 1961-04-26 1963-09-17 Earl G Hedger Fm signal-to-noise monitoring system

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3771059A (en) * 1972-03-27 1973-11-06 Rca Corp Universal data quality monitor
US3885228A (en) * 1973-06-05 1975-05-20 Martin J Katz Fail-safe electronic encoder for selectively operating railway signal indicator
US4092499A (en) * 1975-10-03 1978-05-30 Telefonaktiebolaget L M Ericsson Apparatus for detecting a voice frequency signal
US4019147A (en) * 1975-12-01 1977-04-19 Physics International Company Band pass filter for impulse operation
US4305150A (en) * 1979-05-31 1981-12-08 Digital Communications Corporation On-line channel quality monitor for a communication channel
US4646097A (en) * 1985-05-06 1987-02-24 E-Systems, Inc. Off-channel frequency discriminator circuit for use in a precision distance measuring equipment (DME/P) receiver
US5142526A (en) * 1989-02-15 1992-08-25 Furukawa Electric Co., Ltd. Transmission failure diagnosis apparatus
US20040088611A1 (en) * 2002-11-01 2004-05-06 Broadcom Corporation Methods and systems for detecting symbol erasures
US7080295B2 (en) * 2002-11-01 2006-07-18 Broadcom Corporation Methods and systems for detecting symbol erasures
US20060242478A1 (en) * 2002-11-01 2006-10-26 Broadcom Corporation Methods and systems for detecting symbol erasures
US7765441B2 (en) 2002-11-01 2010-07-27 Broadcom Corporation Methods and systems for detecting symbol erasures

Also Published As

Publication number Publication date
GB1179378A (en) 1970-01-28
CH476428A (de) 1969-07-31
NL6809842A (de) 1969-01-23
BE718315A (de) 1969-01-20
DE1537338B2 (de) 1974-11-14
DE1537338A1 (de) 1969-08-21
FR1574526A (de) 1969-07-11
SE337604B (de) 1971-08-16

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